Vulnerability · Published Mar 18, 2026 · Assigned by GitHub_M
CVE-2026-32728Parse Server has a stored XSS filter bypass via Content-Type MIME parameter and missing XML extension blocklist entries
High 8.3
In plain English
A high-severity cross-site scripting in parse-server from parse-community. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.15 and 8.6.41, an attacker who is allowed to upload files can bypass the file extension filter by appending a MIME parameter (e.g. `;charset=utf-8`) to the `Content-Type` header. This causes the extension validation to fail matching against the blocklist, allowing active content to be stored and served under the application's domain. In addition, certain XML-based file extensions that can render scripts in web browsers are not included in the default blocklist. This can lead to stored XSS attacks, compromising session tokens, user credentials, or other sensitive data accessible via the browser's local storage. The fix in versions 9.6.0-alpha.15 and 8.6.41 strips MIME parameters from the `Content-Type` header before validating the file extension against the blocklist. The default blocklist has also been extended to include additional XML-based extensions (`xsd`, `rng`, `rdf`, `rdf+xml`, `owl`, `mathml`, `mathml+xml`) that can render active content in web browsers. Note that the `fileUpload.fileExtensions` option is intended to be configured as an allowlist of file extensions that are valid for a specific application, not as a denylist. The default denylist is provided only as a basic default that covers most common problematic extensions. It is not intended to be an exhaustive list of all potentially dangerous extensions. Developers should not rely on the default value, as new extensions that can render active content in browsers might emerge in the future. As a workaround, configure the `fileUpload.fileExtensions` option to use an allowlist of only the file extensions that your application needs, rather than relying on the default blocklist.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| npm | parse-server | 9.6.0-alpha.15 | GHSA-42ph-pf9q-cr72 |
| npm | parse-server | 8.6.41 | GHSA-42ph-pf9q-cr72 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| parse-community | parse-server | >= 9.0.0, < 9.6.0-alpha.15< 8.6.41 |
Weakness: CWE-79 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N
References
- https://github.com/parse-community/parse-server/security/advisories/GHSA-42ph-pf9q-cr72 x_refsource_CONFIRM
- https://github.com/parse-community/parse-server/pull/10191 x_refsource_MISC
- https://github.com/parse-community/parse-server/pull/10192 x_refsource_MISC
- https://github.com/parse-community/parse-server/commit/4f53ab3cad5502a51a509d53f999e00ff7217b8d x_refsource_MISC
- https://github.com/parse-community/parse-server/commit/c7599c577a02b97eb5e76d4e20517b0283ae73c8 x_refsource_MISC